Sole for footwear

ABSTRACT

A sole includes a strengthener in the form of a closed loop which surrounds the zone on which the heel rests and is extended forward in the form of two branches extending along the two edges of the sole at least as far as the zone of the first and fifth metatarsal heads.

The subject of the present invention is a sole for footwear which iscurved into the overall shape of a foot or intended to be adapted to theparticular shape of a foot.

It is known practice to use insoles for footwear comprising a surfaceessentially corresponding to that of the bottom of the item of footwearand possibly fitted with localized support and/or shock-absorbingelements. Such soles may be comfort soles or alternatively may be solesintended to improve the stability of the foot or to protect the bonestructure against repetitive shock, particularly for use in sport, suchas walking or running.

The sole according to the invention, which may be an insole or an outersole for footwear, is aimed more specifically at stabilizing the lateralmovement of the foot and at assisting and guiding it in its longitudinalmovement during walking, running or when participating in other sports.

When walking or participating in some sport, a foot unfurls its variouspressure points almost systematically from the outside of the heelforward, passing via the lateral arch and the front of the foot tofinish at the big toe. The path of the barycentres in the dynamics ofwalking describes a curve in the overall shape of an S from the rearforwards and between the outside of the heel and the firstinter-metatarsal space.

The speed of walking, just like the speed of running, depends above allon the duration of the pressure phase.

The pressure time depends on the load-absorbing and energy restitutioncapacity of the anatomical structures. This restitution of energy isassociated with the elasticity of the tissue. Now, most chronic lesionsare due, above all, to the significant forces involved in theload-bearing phase. Furthermore, the kinetic energy generates sheerforces at the surface of the skin, and these are likely to give rise tolesions. Most chronic lesions do not occur during the landing andshock-absorbing phase but during the load-bearing phase, at the momentwhen the foot absorbs the load and flattens by pronation, and when ithas to restore the energy through elasticity of the tissue and muscularcontraction.

The object of the invention is to provide a sole which stabilizes thelateral movement of the foot and guides the latter in its longitudinalmovement so as to increase the elastic reserve of the foot.

To this end, the sole to which it relates, of the aforementioned type,comprises a strengthener in the form of a closed loop which surroundsthe zone on which the heel rests and is extended forward in the form oftwo branches extending along the two edges of the sole at least as faras the zone of the first and fifth metatarsal heads. This strengthenermay form an integral part of the sole or may be attached under the soleand secured to the latter.

The loop-shaped part of the strengthener surrounding the heel isintended to stabilize its lateral movement upon contact with the ground.Specifically, eversion or inversion thereof during this phase leads tothe unfurling of the step shifting off-line during the pressure andpropulsion phases, leading to a loss of energy but also, and above all,to risks of trauma in the foot-knee-back department. The longitudinalbranches of the strengthener make it possible to orientate the unfurlingof the foot and avoid these eversions or inversions of the front of thefoot, and furthermore give rise to a “spoon” effect which encouragespropulsion.

To encourage this “spoon” effect during propulsion, the branch locatedon the inside of the sole extends forward beyond the first metatarsalhead.

According to another feature of the invention, the central zone of thestrengthener located forward of the zone on which the heel rests israised relative to the zones arranged in front of and behind it.

This structure restrains the heel in its forward tilting movement andactually affords a spring effect during the phase of the step serving asa complement of shock-absorbing to the arches and as additional energyrestitution to the “spoon” effect during the propulsion phase.

Advantageously, in its central zone located forward of the zone on whichthe heel rests, the strengthener has two lateral recesses, the far endsof which are set back from the respective lateral edges of the sole.

By virtue of these recesses, the flexible zones of the foot, or arches,are uncovered, which is in keeping with their dynamic functions offlexibility to provide shock-absorbing and restore energy needed for theunfurling of the step.

According to another feature of this sole, the main part of the solecomprises, in the zone on which the heel rests and/or in the zone thatlies between the two branches of the strengthener, an upwards facingbulge corresponding to a downwards facing concave hollow. This is adouble concavity in the transverse direction and in the longitudinaldirection. When the body weight is applied to one or other of these twobulged zones, vertical force tends to tighten the loop in the case ofthe rear bulge, or pull the longitudinal branches together in the caseof the front bulge, thus improving the stabilizing effect.

Advantageously, in order to enjoy a good rigidity/responsiveness ratio,the strengthener is made of a synthetic material or of a compositematerial chosen from polymers, polycarbonates, polycarbolactols orcarbon- or glass-fibre-reinforced resin.

According to a first embodiment, the strengthener is made as a singlepiece obtained by cutting out.

According to another embodiment, the strengthener is made from anelongate single piece bent to form a loop and the ends of which formlongitudinal branches after crossing in the zone located forward of theheel. The crossing of the two branches forward of the zone that takesthe heel forms the desired extra thickness for the heel, and whosefunction was defined earlier.

Furthermore, in the crossing zone the two branches are secured togetheror attached in an elastic and adjustable fashion.

According to another embodiment, the strengthener is made in two partsof which one forms the loop surrounding the heel and the branch locatedon the inside of the sole and of which the other, fixed to the firstpart on the inside of the sole and in the zone forward of the loopformed by the strengthener, extends essentially transversely withrespect to the axis of the sole to meet the outside edge of the sole andform the second longitudinal branch.

Advantageously in this case, the two constituent parts of thestrengthener are made of different materials.

The second part, constituting the longitudinal branch extending alongthe outside of the sole, has an inclined part which forms an angle ofbetween 60 and 90° with the axis known as the metatarsal break, which isthe line along which the front of the foot bends. This orientation ofthe oblique part of the branch allows physiological tilting of the footfrom the lateral to the medial, which makes it possible to acceleratethe way in which the pressure points unfurl and the phase of slowing thefront of the foot, and optimum unfurling of the pressure points toarrive at a pressure point on the big toe, by which the impetus isgiven.

According to one possibility, the ends of the branches of thestrengthener are connected by a bridge, which makes it possible totransfer the body weight more easily from one branch to the other if theweight is bearing too heavily on one of the branches. In order toachieve or improve this realignment effect, at least one of the branchesof the strengthener is equipped with a localized elastic pad or spring.

In any case, the invention will be clearly understood with the aid ofthe description which follows, with reference to the appendeddiagrammatic drawing which, by way of non limiting examples, depicts anumber of embodiments of this sole, in the case of an insole forfootwear:

FIG. 1 is an exploded perspective view of this sole;

FIG. 2 is a perspective view of the various parts of which it is formed,in the assembled position;

FIG. 3 is a view thereof in longitudinal section on III—III of FIG. 2;

FIG. 4 is a view thereof from beneath;

FIGS. 5, 6 and 7 are three views thereof in cross section on V—V, VI—VIand VII—VII of FIG. 3, as the foot is in the course of pressing on theground;

FIGS. 5A and 7A correspond to FIGS. 5 and 7 where the foot is not in thecourse of pressing the illustrated sections to the ground;

FIG. 8 is a view of a second sole from beneath;

FIG. 9 is a view of a third sole from beneath;

FIG. 10 is a view of a fourth sole from beneath.

FIG. 1 depicts an insole 2 for footwear, curved to the overall shape ofa foot or intended to be adapted to the particular shape of a foot. Thissole comprises a main part 3 with a surface corresponding essentially tothat of the bottom of the item of footwear, possibly equipped withlocalized support and/or shock-absorbing elements which have not beendepicted in the drawing. This sole also comprises a strengthener 4which, in the embodiment depicted in FIGS. 1 to 7, is made as a singlepiece, cut and shaped. This strengthener is made of a synthetic materialwith a good stiffness-responsiveness ratio, or of a composite material,for example a carbon- or glass-fibre-reinforced resin. This strengthener4 comprises a loop-shaped part 5 which surrounds the zone on which theheel presses, and which is extended forward by two longitudinal branches6 and 7 arranged along the two edges of the sole at least as far as thezone of the first and fifth metatarsal heads.

As shown in FIG. 4, the branch 7 located on the inside of the soleextends forward beyond the first metatarsal head 8. The central zone 9of the strengthener, located forward of the zone on which the heelpresses, that is to say forward of the loop 5, is raised with respect tothe zones located in front of and behind it, so as to hold the heelfirmly in place and improve performance, as indicated earlier. In itscentral zone located forward of the zone on which the heel presses, thestrengthener has two lateral recesses 10, the far ends of which are setback from the respective lateral edges of the sole. This makes itpossible to uncover the flexible zones of the foot, so as to respecttheir dynamic functions of flexibility.

The main part 3 of the sole comprises, in the zone 12 on which the heelpresses, and in a zone 13 located between the branches 6, 7 of thestrengthener, in each case an upwardly facing bulge 31, 32 correspondingto a downwardly facing concave hollow 41, 42. During walking, pressureis exerted in the zones 12, 13, squashing the bulge 31, 32 and tendingto close the loop, or to pull the branches 6, 7 together, as is shown inFIGS. 5 and 7. FIG. 6 for its part depicts the raised part of thecentral zone 9 of the strengthener which holds the heel in place. Asshown in particular in FIG. 4, the branch 6 on the one hand has alongitudinal part and, on the other hand, forms an oblique line betweenthe part located forward of the loop and on the inside of the sole andthe part on the outside of the sole. This oblique line 14 makes an angleof between 60 and 90° with the bend line 15 of the front of the foot, ormetatarsal break, this oblique line allowing the foot to tiltphysiologically from the lateral to the medial to ease and guide theunfurling of the pressure points.

FIG. 8 depicts a second embodiment in which the strengthener is made ofan elongate piece in the form of a band which is bent round on itself toform a loop 16, and the free ends of which form the longitudinalbranches 17 and 18. The zone 19 where the two branches cross forms theextra thickness which provides the support forward of the heel. It maybe noted that, when it is bent round to form a loop, the band inclinesfrom the inside outward and from the bottom upward in the zone thataccommodates the heel, which encourages guidance thereof.

FIG. 9 depicts another embodiment in which the strengthener is made intwo parts, that is to say a part 20 forming a loop 22 extended by a part23 forming a longitudinal branch located on the inside of the sole. Thestrengthener comprises a second part 24, which forms an oblique partextending from the inside edge of the sole, in the region locatedforward of the loop 22, to the outside edge of the sole in the zone ofthe fifth metatarsal. The part 24 is fixed to the part 20 and may, forexample, be made of a different material from the material of which thepart 20 is made, for example of a material which is more rigid toencourage the effect of tilting about the previously defined obliqueaxis.

FIG. 10 depicts a sole which is an alternative form of the one in FIG. 8and in which the same elements are denoted by the same references asbefore. In this sole, the ends of the branches 17, 18 are connected by abridge 25 allowing the body weight to be transferred onto the otherbranch if the weight is exerted too heavily on one of them. Furthermore,the underside of the branch 17 is equipped with an elastic pad 26encouraging this effect of realigning or transferring the body weightonto the other branch.

As is evident from the foregoing, the invention provides a greatimprovement to the known art by supplying an insole for footwear whichprovides the foot with lateral stability, guides it in its longitudinalmovement while at the same time encouraging propulsion, absorbingshocks, allowing venous drainage and an effect of massaging the sole ofthe foot, and above all assisting the foot in the restitution of itselastic reserve.

As goes without saying, the invention is not restricted simply to theembodiments of this sole which have been described hereinabove by way ofexample; on the contrary it encompasses all alternative forms thereof.Thus, in particular, the strengthener could be made not independently ofthe body of the sole and fixed under this sole later, but form anintegral part of the body of the sole or, alternatively, thestrengthener could be incorporated into the main sole of the item offootwear without in any way departing from the scope of the invention.

What is claimed is:
 1. Sole for footwear, curved into the overall shapeof a foot or intended to be adapted to the particular shape of a foot,of the type comprising a surface essentially corresponding to that ofthe bottom of the item of footwear and capable of being fitted with atleast one of localized support and shock-absorbing elements, the solecomprising: a strengthener in the form of a closed loop which surroundsa zone on which the heel rests and is extended forward in the form oftwo branches extending along two edges of the sole at least as far as azone of first and fifth metatarsal heads, wherein the strengthener ismade from an elongate single piece bent to form a loop and having endswhich form two longitudinal branches after crossing in a crossing zonelocated forward of the heel.
 2. The sole of claim 1, wherein a branchlocated on an inside of the sole extends forward beyond the firstmetatarsal head.
 3. The sole of claim 1, wherein a central zone of thestrengthener located forward of the zone on which the heel rests israised relative to zones arranged in front of and behind it.
 4. The soleof claim 1, wherein in the central zone, the strengthener has twolateral recesses, the two lateral recesses having far ends which are setback from respective lateral edges of the sole.
 5. The sole of claim 1,wherein a main part of the sole comprises, in at least one of the zoneon which the heel rests and a zone that lies between the two branches ofthe strengthener, an upwards facing bulge corresponding to a downwardsfacing concave hollow.
 6. The sole of claim 1, wherein the strengtheneris made of a synthetic material or of a composite material chosen from agroup consisting of polymers, polycarbonates, polycarbolactols orcarbon- or glass-fibre-reinforced resin.
 7. The sole of claim 1, whereinthe strengthener is made as a single piece obtained by cutting a shapefrom a larger piece.
 8. The sole of claim 1, wherein the ends of thebranches are connected by a bridge.
 9. The sole of claim 1, wherein atleast one of the branches is equipped with a localized elastic pad orstring.
 10. The sole of claim 1, the two branches are secured togetheror attached in an elastic and adjustable fashion in the crossing zone.11. Sole for footwear, curved into the overall shape of a foot orintended to be adapted to the particular shape of a foot, of the typecomprising a surface essentially corresponding to that of the bottom ofthe item of footwear and capable of being fitted with at least one oflocalized support and shock-absorbing elements, the sole comprising: astrengthener in the form of a closed loop which surrounds a zone onwhich the heel rests and is extended forward in the form of two branchesextending along two edges of the sole at least as far as a zone of firstand fifth metatarsal heads, wherein the strengthener is made in twoparts of which a first part forms the loop and a branch located on aninside of the sole and of which a second part, fixed to the first parton the inside of the sole and in a zone forward of the loop formed bythe strengthener, extends essentially transversely with respect to anaxis of the sole to meet an outside edge of the sole and form the secondlongitudinal branch.
 12. The sole of claim 11, wherein the two parts ofthe strengthener are made of different materials.
 13. The sole of claim11, wherein the ends of the branches of the strengthener are connectedby a bridge.
 14. The sole of claim 11, wherein at least one of thebranches of the